The present invention relates to a control system for an electrophotographic copier, printer, facsimile transceiver or similar image forming equipment.
Image forming equipment of the kind described has many kinds of image forming control that have to be executed in parallel. Microprocessors, which commonly execute only one type of control task at a time, cannot deal with a plurality of image forming tasks in parallel unless there is provided some device for parallel processing of various individual image forming control programs. In addition to increasing the cost of image forming equipment, an increasing demand for providing a greater number of control functions requires systems to be more complex. A current trend is, therefore, toward modular control, i.e., replacement of single complicated control with a collection of simple control modules. For modular control, various kinds of image forming control are allocated to a plurality of microprocessors or assigned to exclusive hardware. However, a control system using different kinds of hardware is expensive. Regarding a plurality of microprocessors, for example, each microprocessor has to be provided with exclusive peripheral devices such as a memory and, in addition, the whole system involves many redundant portions since the contents of control are the same. When the capacity of programs is increased or the control system is changed, the same program correction has to be effected a plurality of time due to the redundancy particular to the above-mentioned system, resulting in inefficient maintenance. While a one-chip processor having a single master processor and a plurality of slave processors is available today, it also has the problems described above since it uses a plurality of processors. Another and more serious problem with the one-chip processor is that it cannot cope with larger numbers of objects to control, e.g. paper sheets.